The cost of...

Despite what theologians and conspiracy theorists might say, the search for extraterrestrial life is just a numbers game. The likelihood of alien life existing is dependent on the number of other planets in solar systems beyond ours. If there are an infinite number of solar systems, each with its own planets, then it is statistically quite possible that somewhere, some time, there will be life other than us.

The trick is to find it. The two most valid techniques are to listen and to look. Looking for planets, the first step, requires a telescope. For amateur astronomy, expect to spend at least £250 on a good telescope. Ideally you want your telescope to pick up the distortion in the light spectrum caused by an undiscovered planet. Something like Ukirt - the United Kingdom Infra-Red Telescope, conveniently located in Hawaii - will do the job. The world's largest observatory, a £250m project codenamed Alma, is being built on the Atacama plateau in the Andes. Or buy something like the solar-powered Hubble Telescope, which recently underwent a service in space. At its launch in 1990, Hubble cost $2.2bn; thankfully there aren't any fuel bills.

Listening for alien life is a similar process. Radio waves from space are collected by receivers worldwide and analysed for anomalies that might give away aliens. The Seti - Search for Extra-Terrestrial Intelligence - project harnesses the unused processing power of home computers to do this work. Simply download some free software and your computer will be quietly hunting down other lifeforms as you work. The Seti League's Project Argus encourages amateurs to build their own satellite-receiver units, which will then monitor the skies as a whole network. You will need one satellite dish ($2,000), a feedhorn ($50), a microwave receiver ($2,000), some coaxial cable and a home computer. Buy the kit second-hand for about $1,000.

The least scientific technique is to wait for extraterrestrials to come to you. The highest concentration of sightings is in Nevada. There are plenty of $40-per-night motels along Highway 375 (officially the Alien Highway) and flights to Las Vegas are about £250.